Re: [PATCH 1/2] block: RCU protect disk->conv_zones_bitmap

[Damien Le Moal <dlemoal@kernel.org>]

On 11/7/24 14:40, Christoph Hellwig wrote:
> As sparse rcu warnings got in my radar for something else, I did
> run sparse over this and it complains.  It will need the little
> gem below to fix (and a rebase of the second patch).  Otherwise the
> series looks great and way better than my initial hack, thanks!

OK. I will integrate this and send v2.

> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 7a7855555d6d..bf4458b11720 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -350,11 +350,12 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
>  
>  static inline bool disk_zone_is_conv(struct gendisk *disk, sector_t sector)
>  {
> +	unsigned long *bitmap;
>  	bool is_conv;
>  
>  	rcu_read_lock();
> -	is_conv = disk->conv_zones_bitmap &&
> -		test_bit(disk_zone_no(disk, sector), disk->conv_zones_bitmap);
> +	bitmap = rcu_dereference(disk->conv_zones_bitmap);
> +	is_conv = bitmap && test_bit(disk_zone_no(disk, sector), bitmap);
>  	rcu_read_unlock();
>  
>  	return is_conv;
> @@ -1467,11 +1468,10 @@ static unsigned int disk_set_conv_zones_bitmap(struct gendisk *disk,
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
> +	if (bitmap)
> +		nr_conv_zones = bitmap_weight(bitmap, disk->nr_zones);
>  	bitmap = rcu_replace_pointer(disk->conv_zones_bitmap, bitmap,
>  				     lockdep_is_held(&disk->zone_wplugs_lock));
> -	if (disk->conv_zones_bitmap)
> -		nr_conv_zones = bitmap_weight(disk->conv_zones_bitmap,
> -					      disk->nr_zones);
>  	spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
>  
>  	kfree_rcu_mightsleep(bitmap);


-- 
Damien Le Moal
Western Digital Research